Aqueous rubber dispersion and process of producing the same



Patented Mar. 15, 1927.

wnmnm mason rm'rr, or WELLESLEY, msssaonusnrrs, assreuon 'ro'-nnsnsa'cn,

mconrona'rnn, or BOSTON, massaonusn'r'rs, a-conrom'rxorr or unssacnu-SE'I'TS.

AQUEOUS aunnnamsrnnsron m1) rnocnss or .rn'onucme 'rmz: same.

In Drawing,

This invention has relation to aqueous difi'usions, dispersions oremulsions of crude or previously coagulated rubber, or synthetic rubber,or unvulcanized' rubber compounds, such as generally referred to in myapphcation' Serial No. 604,616, filed December 2,

' 1922, and also in my application Serial No.

631,451, filed April 11, 1923.

I have made the discovery that it is pos .sible to diffuse, disperse oremulsify crude r previofisl y coagulated'. rubber, and kmdr tlsubstances, in water without the employment of soap produced bythereaction of an alkali or alkaline material, such as a caustic alkali orammonia with a. saponifiable agent. That is tosay, I have discoveredthat It is possible to effect a dispersion of the rubber or rubbercompound inwater'by'the use of a saponin, or what maybe called a naturalvegetable soapy substance. Instead of using saponin in a substantiallypure form, I

' have found that I ma with even greater as This advantage, employ ast eemulsifying agent an-aqueous extract or infusion of. soap bark. I reard. as highly advantageous not only for t e purposes of economy, as itenables me to dispense with the employment of relatively expensivesaponifiable agents,

1 such as fatty acids, or the glycerides of fatty acids, but alsobecause it avoids the presence of any alkali or alkaline matter in theaqueous rubber dispersion; and, consequently, the aqueous rubberdispersion or emulsion may be concentrated to the desired extent withoutcoagulation of the rubber globules and without deleterious effect on thesubsequent vul-. 'caniz'ation. 1 f

, In carrying'out this process;crude ..rubber or the crude rubbercompound may be pri.-'

marily converted'into a colloidal solution, so far as the rubber isconcerned, by the use of a solvent of the aromatic orcarbo-cyclic series, such as benzene (C H that commer-.

cial mixture known as benzol, toluol or their equivalent. Afterthedispersion is efi'ected,

the solvent is removedand'pr f bl covered forreuse.

As illustrating an example of the pro c'edure which may be followed inthe prac"- tice of my invention, 35 pounds of crude 'rubber, e.- g. thatobtained from Hebea Brazilz'ensz's, is dissolved in pounds-of commercial'benzol to solution. This is v ected by 'achurn or me Application filedJuly 2,

reduce a- 35% colloidal 1923. Serial 110,649,158.

chanical mixer, and the product-is substantially a physicallyhomogeneous paste. I

now dissolve about 1.7 5- pounds of saponin in the stirringiprocee s,the water, which firstforms the sperse phase, with the continuedstirring soon forms the continuous phaseiof the dispersion or emulsion.Instead of mix ing thewater into and with the rubber-ben- 201 solution,the latter may be stirred into and mixed with the water. The benzol re.-

maining in the product is removed by distillation or evaporation,referably under a vacuum, soas to avoid t e use of excessive heat suchas would tend to cause .the recoagulat-ion of the rubber. In theresultingprodnot, the rubber apparently has been entirely decoagulatedand dispersed and the dispersed rubber globules are apparently of thesame size and form as in the latex from which the crude rubber wascoagulated.

'Instead of dispgrsing crude rubber alone in Water, the rub r may'be'previously compounded with sulphur, zinc oxide, comfner- J a cialmineral rubber, commerclal accelerator,

and other compounding materials, as may be.

desired, so that in the subsequent vulcanizing process the vulcanizedrubber of any particular character may be, secured. Thus any of thecommercial rubber compounds may be' first produced by milling and thendispersed in water by the process hereinbefore outlined. Those materialswhich are not dissolved or emulsified are distributed through 'the finalaqueous rubber dispersion.

The dispersed mass produced in either case after the removal of thebenzol maynow be concentrated bythe removal of more or le s of thevegetable soap-like substance and the water, and to that end the massmay be placed in a centrifuge and subjected to ,cens trifugation. Acentrifugal machine of the.

character of a cream separator may be emtion of the'water anthe'soap-like. substance, which may be effected several times or inseveral steps by diluting with water the result ick ployed for this puose. After the separaing diffusion, a thickpasty mass may bev lproiduced having the general character of a t smooth mud formed of smoothclay and water, and in this paste the rubber particles or globules arenot coagulated but are dis-' tion 1s homogeneous, non-tacky, spreadsevenl and does not coagulate on standing,

nor the solids separate from the water. in

. commercial application.

.the extract of soap; bar

min, I find that I may use a much less expensive vegetable soapsubstance, namely,

ii and that a smaller quantity of the extract,.say 1%, may beemployed'than when saponin is used in a substantially pure toning-Anysuitable procedure for extracting the '-soap bark in water may befollowed; for example, equal quantities by weight of soap barkand watermay ,be heated to atemperature less than the boiling point of water, fora short time,

say twenty minutes, after which the watercontaining the extract isdecanted. The soap bark may be-again extracted with an equal amount ofwater. The extract in each case contains the act ve principles of theThe saponin and the soap bark extract apparently have the best effect inreducing the interfacial tension of the benzol, the benzol-saturatedrubb'er globules and the water, and make it possible to secure a dispersion of the rubber globules with great easewhen the water'andrubber-benzol solution are mixediin'fthe presence thereof.

,The soa'p bark extract, if desired, may

be dried to powder form and. the. powder dissolved in water for makingthe aqueous rubber dispersion.

So 'far as I am,.aware, Iain. the to have discovered that-the-product ofextraction from such vegetable compounds may be employed, with water asan emulsifying agent, in dispensing crude or coagu ate rubber orkindred. products in water; and in the claims, in referring tosoapyvegetable e xtracts, I-mean to include saponins, r a as well-"asextracts from soap bark? so called. w

; V I have formed the o inion that, when re- -viously coagulated ruber'or crude r'u is treated with, a-solventi benzol for esam le, to forma colloi a1. solution,-'-co nzol, the globules tend to and actually dofacial tension --is reduced. Hence,in order the interfacial tension ofthe 'globules'. I

. have ioundthat-the best results are secured: .i when thatsubstance .isemployed which has menace of the benzol .from the aqueous dispersion aswell as to prevent the rubber globules from cohering or coagulating asthey shrlnk in size due to the removal of benzol previously absorbedthereby. Instead of. using substantially pure sapo- In the initialcolloidal benzol -rubber solution, the swollen rubber globules aresticky,

and any finely divided substances which were in admixture with therubber (such for example as sulphur, zinc oxide, whiting and v the like)attach themselves in the form of fineparticles to the rubber globules.Subsequently, when the aqueous dispersion is effected and the benzol isremoved, there appearsto be an adhesion of the fine particles to therubber globules which ensures the distribution of such particlesthroughout the mass. Prior to the concentration of the dispersion, ifthere be no addition of [relatively heavy compounding materials,

the separation'of the rubber globules and the compounding agents fromthe Water is easily effected by well known processes.

What I claim is 1. A process of dispersing rubber in water, whichcomprises dissolving rubber in a.

solvent, then mixing such solution with water in the presence of a soapyvegetable extract whereby the rubber globules are dis- Ipersed in theaqueous medium, without breaking down the physical structure of theglobules, and finally removing the solvent l'without recoagulating thedispersed rubber globules. l

'2. A-- process of dispersing rubber in water, which comprisesdissolving rubber in a solvent, mixing the solution with water con- Vtaming-a-soapy vegetable extract, then mixirg-"the resultingomassandwater so that the water forms the continuous base of the dispersionor emulsion, and the ecoagulated" rubber globules are dispersed therein,withp out afi'ecting the physical structure 'of the incidently with. theswellmg of the rubber lobules, due Ito'their absorption of 'the'globules. separate from each other as their globules, and finallyremoving the solvent without recoagulating the dispersed rubber 1. .3.3! process of dispersing in water an unvulcanized rubber compound,including rubber and sulphur, which comprises first compounding "saidmaterials, mixing the compound wlth a rubber-solvent, dispersing the;:product in water in the presence of a so y y egetable extract, whereinthe rubber si'gliiiiules'approximate thesize andsha e of therubberglobules in latex, and fina yTremoving the solvent withoutrecoagulating the dispersed rubber globules.

4. A process of dispersing rubber in water, which comprises dissolvingrubber in a solvent, then mixing such solution with water in thepresence of a soapy vegetable extractwhereby the rubber globules aredising the resulting mass and water until the water forms the continuousphase of the dispersion or emulsion, and the decoagulated rubberglobules are dispersed therein, and

removing said solvent Without coagulating the rubber globules, therebyleaving the i'lublber globules dispersed in the aqueous veic e.

6. A process of dispersing rubber in w ter, which com rises dissolvingrubber in asolvent, then mixing such solution with water in thepresenceof a soapy vegetable extract whereby the rubber globules aredispersed in the aqueous medium, removing the solvent, and concentratingthe product by removal of water until a smooth paste results.

7. A process of dispersing rubber in water, which comprises dissolvingrubber in a solvent, mixing the solution with water containing a soapyvegetable extract, then mixing the resulting mass and water so that thewater ,forms the continuous phase of the dispersion or emulsion, and thedecoagulated rubber globules are dispersed therein, removing saidsolvent, and. concentrating .the resultant product b removal of wateruntil a smooth paste resu ts, all withoutrecoagula- -tion of the rubberglobules.

8. A process of dispersing in water an unvulcanized rubber compound,including rubber and sulphur, which comprises fir'st compounding saidmaterials, mixing the compound with a rubber solvent, dispersing theproduct in water in the presence of a soapy vegetable extract, andremoving the rubber solvent, thereb leaving the rubber globulesdispersedin t e aqueous vehicle. A

9. A process of dispersing in water an unvulcanized I rubber compound,including rubber and sulphur, which comprises first compounding saidmaterials, mixing the compound with a rubber solvent, dispersing theproduct in water in the resence of a soapy vegetable extract, removinthe rubber solvent, and finally removing su cient water to leave asmoothpaste without recoagulating the rubber globules, which approximate insize and shape the rubber of latex.

10. A process of dispersing unvulcanized rubber in water, which comrises dissolving such rubber in a rubber so vent, and mixing thesolution with water, in thepresence of an extract of soap bark, untilthe rubber is dispersed in the water in separated globules.

11. A process rubber in water, such" rubber in a rubber solvent, mixingthe solution with water, in the presence of an extract of soap bark,until the rubber is dispersed in the Water, and removing the solvent.12. A process rubber in water, such rubber in a rubber solvent, mixingthe solution with water, in the presence of an extractiof soap bark,removing the solvent, audthen concentrating the product to the form of asmoothpaste without recoagulating the rubber globules, which approximatein size and shape those in rubber latex.

In testimony whereof I have aflixed my signature.

of dispersing unvulcanized of dispersing unvulcanized which comprisesdissolvingwhich comprises dissolving

